Upflow coal liquefaction

ABSTRACT

COAL IS LIQUEFIED WITHOUT EMPLOYING INTERNAL MIXING (BY STIRRERS, ETC.) IN A TURBULENCE-FREE UPFLOW LIQUEFACTION ZONE, PROVIDING IMPROVED YIELDS AND SELECTIVITY OF DESIRABLE LIQUID PRODUCTS THAN A WELL-MIXED LIQUEFACTION ZONE. BEFORE INTRODUCTION TO THE UPFLOW LIQUEFACTION ZONE, A SLURRY OF THE COAL IN A HYDROGEN-DONOR SOLVENT IS PREHEATED TO A TEMPERATURE WITHIN THE RANGE FROM ABOUT 700*F. TO ABOUT 900%F. AND SUBJECTED TO CONDITIONS OF TURBULENCE, A TREATMENT WHICH CAUSES THE COAL PARTICLES, ESPECIALLY CAKING-TYPE COAL PARTICLES, TO DISINTEGRATE WITHOUT AGGLOMERATION. INTRODUCED INTO A LOWER PORTION OF THE LIQUEFACTION ZONE, THE COAL, IN MIXED SOLID AND LIQUID PHASE, IS PLUG FLOWED UPWARDLY AT A SUPERFICIAL LIQUID VELOCITY SUFFICIENT TO CARRY UPWARD ALL PARTICLES WHICH HAVE A MAXIMUM SETTLING VELOCITY OF FROM ABOUT 0.01 TO ABOUT 0.04 FT./SEC. PARTICLES OF HIGHER SETTLING VELOCITIES SETTLE THROUGH THE ZONE. CONTINUED DISSOLUTION OF LARGE CONVERTIBLE COAL PARTICLES DECREASES THEIR SIZE UNTIL THEY TOO RISE THROUGH THE LIQUEFACTION ZONE. SETTLED ASH-FORMING PARTICLES ARE REMOVED FROM A LOWER PORTION OF THE ZONE. A LIQUEFACTION PRODUCT IS REMOVED FROM AN UPPER PORTION OF THE ZONE. THE LIQUEFACTION PRODUCT CONTAINS FROM ABOUT 70 TO ABOUT 96 WEIGHT PERCENT OF MEK SOLUBLE MATERIALS. SOLIDS RECOVERED FROM A LOWER PORTION OF THE LIQUEFACTION ZONE CONTAIN FROM ABOUT 25 WEIGHT PERCENT TO ABOUT 35 WEIGHT PERCENT OF MEK INSOLUBLES AND FROM ABOUT 35 TO ABOUT 45 WEIGHT PERCENT OF ASH. CONDITIONS IN THE LIQUEFACTION ZONE INCLUDE A TEMPERATURE WITHIN THE RANGE FROM ABOUT 700*F. TO ABOUT 100*F., A PRESSURE WITHIN THE RANGE FROM ABOUT 350 P.S.I.G. TO ABOUT 3000 P.S.I.G. AND AN AVERAGE LIQUID RESIDENCE TIME WITHIN THE RANGE FROM ABOUT 5 MINUTES TO ABOUT 60 MINUTES. THE HYDROGEN-DONOR SOLVENT MAY BE SUPPLEMENTED WITH FROM ABOUT 0.1 TO ABOUT 10 WEIGHT PERCENT OF HYDROGEN IN GASEOUS FORM IN THE LIQUEFACTION ZONE. PREFERRED HYDROGEN DONORS INCLUDE INDANE, C10-C12 TETRALINS, C12 AND C13 ACENAPHTHENES, DI-, TETRA-, AND OCTAHYDROANTHRACENE, AND TETRAHYDROACENAPHTHENE.

Feb. 29, 1972 Filed May 4,. 1970 4 Sheets-Sheet l SLURRY RHEO LOGICALBEHAVIOR 45 WT. COAL/HYDROGENATED CREOSOTE OIL SLUR RY HYDROGENATIONzone 34 S/C i2 N Cool Type Illinois No.6

3 Cool SizeMinus lOOMesh 3 Moisture Conienti-34 (Wi.)/ I 8 Temperature5.42F.(Ai Equilibrium) Pressure 420 psiu a m w E m m 1 1 LL] :7;

IOO

I l l l I l l i l i i l 0 I00 200 300 FIG. 4. SHEAR RATE,SEC 28 GASESCOAL NAPHTHA :38

UPFLOW 26 GAS-LIQUID HYDROGEN-DONOR ggijg s5 PA RATOR SOLVENT l2 if mxme39 ZONE 24 FRACTIONATING STRIPPING ZONE ZONE 3| 29 GAS I6 30 32 2I-NAPHTHA i 23 34 PREHEATING ZONE 25 ASHFORMING 33 HEAVY souos GAS on.

INVENTORS. GRADY W. HARRIS BY FRANK B. SPROW,

ATTORNEY.

Feb. 29, 1972 w HARRIS ETAL 3,645,885

'UPFLOW COAL LIQUEFACTION Filed May 4, 1970 4 Sheets-Sheet 2 EFFECT OFTEMPERATURE ON VISCOSITY 45 WT.% COAL/HYDROGENATED CREOSOTE OIL SLURRYs/c-|.2 24 Min. 3 Cool Typ '-lllinois No. 6 T i Coal Size Minus IOO MeshMoisture Conienil.34 (W'r.)% r ShearRaie 289 sec- IHr. at v 654F.

T' =07 50- i i- I 6 Time=|8. 5 Min. 0 U m K Newtonian Non-NewtonianBehavior Behavior 5 l I i 1 TEMPERATURE ,F.

FIG. 2.

INVENTOR.S. GRADY W. HARRIS, FRAN B. SPROW,

ATTORNEY.

Feb. 29, 1972 UPFLOW 00 Filed May 4, 1970 VISCOSITY,CP

G. W. HARRIS E-TAL AL LIQUEFACTION 4 Sheets-Sheet 5 NON NEWTONIANBEHAVIOR OF 45 WT.% COAL/HYDROGENATED CREOSOTE OIL SLURRY AT 542 F.

IOOO

Coal Type Illinois No.6

Cool Size Minus I00 Mesh 800 1 Moisture Content I. 34 (W1.

7OO Shear Ruie Viscosity (Sec") (CP) 600 I6 783 BZI O l I l 1 l i l i il l SHEAR RATE,SEC"

FIG. 3.

INVEN'IORJ.

GRADY w HARRIS,

FRANK B. SPROW ATTORNEY Feb. 29, 1972 I I G. w. HARRIS ETAL 3,645,885

UPFLOW COAL LIQUEFACTION Filed May 4, 1970 4 Sheets-$heet 4.

INFLUENCE OF TEMPERATURE ON VISCOSITY 45 WT./o COAL/HYDROGENATEDCREOSOTE OIL I I I I Sample Shear Rafe ViscosH/F H\ T MB (5%) (CPI I8Min.

868 Cu? OF I I Scale For 0 5Min. I

( 7OCP) 7 I45 2|O 5o- I Cool Type-Illinois No.6 g- Cool Size Minus I00Mesh Shear Rate 868 Secf 40 8 32Mln.' o (n 5 Sample TE HEATING lo I OCOOLING \Q Sample zzmh, .ATSTIF o IP- *I'l -'I I 200 300 400 500 600 700TEMPERATURE ,F.

FIG. 5.

INVENTORS,- GRADY w. HARRIS, BY FRANK B.sPRow,

ATTORNEY.

United States Patent O 3,645,885 UPFLOW COAL LIQUEFACTION Grady W.Harris, Cambridge, Mass., and Frank B. Sprow,

Houston, Tex., assignors to Esso Research and Engineering Company FiledMay 4, 1970, Ser. No. 34,224 Int. Cl. C10g 1/04 US. Cl. 208-8 12 ClaimsABSTRACT OF THE DISCLOSURE Coal is liquefied without employing internalmixing (by stirrers, etc.) in a turbulence-free upflow liquefactionzone, providing improved yields and selectivity of desirable liquidproducts than a well-mixed liquefaction zone. Before introduction to theupliow liquefaction zone, a slurry of the coal in a hydrogen-donorsolvent is preheated to a temperature within the range from about 700 F.to about 900 F. and subjected to conditions of turbulence, a treatmentwhich causes the coal particles, especially caking-type coal particles,to disintegrate without agglomeration. Introduced into a lower portionof the liquefaction zone, the coal, in mixed solid and liquid phase, isplug flowed upwardly at a superficial liquid velocity sufficient tocarry upward all particles which have a maximum settling velocity offrom about 0.01 to about 0.04 ft./sec. Particles of higher settlingvelocities settle through the zone. Continued dissolution of large convertible coal particles decreases their size until they too rise throughthe liquefaction zone. Settled ash-forming particles are removed from alower portion of the zone. A liquefaction product is removed from anupper portion of the zone. The liquefaction product contains from about70 to about 96 weight percent of MEK soluble materials. Solids recoveredfrom a lower portion of the liquefaction zone contain from about 25weight percent to about 35 weight percent of MEK insolubles and fromabout 35 to about 45 weight percent of ash. Conditions in theliquefaction zone include a temperature within the range from about 700F. to about 1000 F., a pressure within the range from about 350 p.s.i.g.to about 3000 p.s.i.g. and an average liquid residence time Within therange from about minutes to about 60 minutes. The hydrogen-donor solventmay be supplemented with from abouut 0.1 to

about 10 weight percent of hydrogen in gaseous form in the liquefactionzone. Preferred hydrogen donors include indane, C -C Tetralins, C and Cacenaphthenes, di-, tetra-, and octahydroanthracene, andtetrahydroacenaphthene.

BACKGROUND OF THE INVENTION This invention involves the production ofliquid hydrocarbon products from solid coal, and more particularly, thestep in such a process which utilizes a hydrogen-donor solvent in theliquefaction zone.

Heretofore, as illustrated by US. Pats. 3,018,241, 3,075,912 and3,117,921, liquefaction of solid coals utilizing a hydrogen-donorsolvent has been carried out in a well-mixed reactor using stirrers,agitators etc. with attendant problems of costly power consumption andassociated mechanical difliculties. In these reactors, incompleteliquefaction of larger convertible coal particles commonly occurs,particularly in continuous process operations. In addition, extensiveand costly mechanical separations equipment has to be used downstream ofthe 3,645,885 Patented Feb. 29, 1972 liquefaction zone to separate theunliquefied convertible coal and nonconvertible coal solids from theliquefied product. All of this contributes greatly to the cost ofrecovering liquid hydrocarbon products from solid coal. Representing arecent attempt to escape these difliculties, US. Pat. 3,488,278 suggeststhat ground coal particles be settled through a countercurrent stream ofsolvent (and hydrogen gas) flowed upwardly at increasing velocitieseffected by vertically-staged solvent inlets. This approach, however,falls short of overcoming the aforesaid difiiculties in a mannerproviding materially improved economies of operation. It is thereforehighly desirable and plainly important that the difficulties andshorcomings in the present level of the art of liquefying coal using ahydrogen-donor solvent be reduced or eliminated.

SUMMARY OF THE INVENTION Liquefaction of coal in a hydrogen-donorsolvent is accomplished without internal mixing in the liquefaction zonein a continuous new process which provides improved yields andselectivity in the liquefaction of convertible coal and which minimizesthe presence of ashforming particles in the liquefaction product.According to this process, the coal in particulate form and slurried ina hydrogen-donor solvent is prepared for plug flow in a turbulence-freeupflow liquefaction zone by preheating the slurry to a temperaturesufiiciently high to cause the slurried coal particles to disintegrateand partially dissolve while subjecting the heated slurry to turbulenceto prevent particle agglomeration. The preheated coal slurry in mixedsolid and liquid phase is then introduced into a lower portion of anupflow liquefraction zone and passed upwardly under conditions ofnonturbulent plug flow at a superficial liquid velocity sufficient tosupport coal fines and to permit the settling of heavier particles.Conditions in the liquefaction zone include a temperature high enough topermit a hydrogen-transfer reaction between the hydrogen-donor solventand moistureand mineral-free portions of the coal, a pressure highenough to prevent appreciable vaporization of the solvent, and anaverage liquid residence time sufiicient to produce a liquefactionproduct in an upper portion of the reaction zone. The liquefactionproduct is withdrawn from an upper portion of the liquefaction zone andcontains from about to about 96 Weight percent of methyl-ethyl ketone(MEK) soluble materials. Settled solids are withdrawn from a lowerportion of the liquefaction zone. These solids consist essentially offrom about 25 to about 35 weight percent of MEK insoluble materials andfrom about 35 to about 45 weight percent of ash-forming materials. Thusin addition to a better yield and selectivity than a well-mixedliquefaction zone, the high ash concentration of the solids withdrawnfrom the lower portion of the zone reduces the load on downstream solidsremoval equipment and eliminates expense in mechanical separationsequipment to remove essentially unconvertible parts of the coal.

For a better understanding of the present invention, each of the aspectsof the complete overall process scheme will be separately discussed.

Preparation of the coal The basic feedstock to the process of thepresent invention is a solid, particulate coal such as bituminous coal,subbituminous coal, lignite, and brown coal, or a mixture thereof.Although it is desirable to grind the coal to a particle sizedistribution from about 8 mesh and finer, it has been found that thepreheating treatment hereinafter described and the solvation reactioncarried out in the liquefaction zone will result in adequate conversioneven if particles as large as one-fourth inch on the major dimension arecharged to the preheating zone. The preheating treatment is especiallyuseful for cakingtype coals, as hereinafter described in greater detail.A typical proximate and ultimate analysis of an Illinois No. 6 coal (acaking-type Eastern bituminous coal mined in Macoupin County, Illinois)and of Gillette coal (a noncaking type Western subbituminous coal minedin Campbell County, Wyoming) which have been utilized in this process isset out in Table I, which follows:

TABLE I.CHEMICAL ANALYSIS OF COAL WT. PERCENT DRY ANALYSIS Illinois coalThe coal preferably is dried to remove excess water, although it isfeasible to utilize coal which is not moisture free if the liquefactionfacilities have been sized to allow the withdrawal of evolved steam. Thecoal can be dried by convention techniques prior to mixing it with thehydrogen-donor solvent to form the slurry feed for liquefaction. It ispreferred, however, to mix the wet coal with a hot hydrogen-donor oil ina mixing zone to volatilize water in the mixing zone, thereby reducingthe feed slurry moisture content to less than about two weight percent.Thus, the mixing zone also serves the function of a drier zone.

Hydrogen-donor solvent In the mixing zone, the coal feedstock at ambienttemperature is mixed with a hydrogen-donor solvent which has atempeature of from about 500 F. to about 700 F. The solvent/coal weightratio is within the range from about 0.8:1 to about 2: 1, resulting in aslurry temperature within the range from about 300 F. to about 350 F. Amechanical propeller or other agitating device may suitably be providedin the mixing zone to obtain a uniform slurry concentration.

The hydrogen-donor solvent boils within the range from about 300 F. toabout 900 F., preferably from about 375 F. to about 800 F., atatmospheric pressure, so as to remain in the liquid phase at theelevated temperatures employed in the liquefaction zone. Desirably, thesolvent will contain at least 30 weight percent, preferably at least 50weight percent, of compounds which are known to be hydrogen donors underthe conditions used in the liquefaction zone. The hydrogen-donor solventstream suitably contains one or more hydrogen-donor com-pounds inadmixture with non-donor compounds or with one another, compounds suchas indane, C -C Tetralins, C and C acenaphthenes, di-, tetra-, andoctahydroanthracene, and tetrahydroacenaphthene being preferredhydrogen-donor compounds, as are other derivatives of the partiallysaturated hydroaromatic compounds.

It is preferred that the solvent stream be a hydrogenated recyclesolvent fraction. The composition of such a fraction will vary somewhat,depending upon the source of the coal used as the feedstock to thesystem, the operating conditions in the overall process, and theconditions used in hydrogenating the solid fraction for recycle afterliquefaction. However, a typical description of a hydrogenated recyclesolid fraction will be simiar to that shown in Table II.

TABLE Ill-TYPICAL RECYCLE SOLVENT Distillation-Glass spiral Cumulativewt. percent over Sp. git, 60 F./60 F.

Temp.,F.-760 mm.

Mass spec. analysis W t Typical compound percent Elemental analysisCarbon Hydro gen Oxygen CHEM-6 Alkylbenzene--. O nHh-B Tetralin CnHZnl-O Indene OnH2n'l-2 Naphthalene" Gn 2u' Acenaphthene-.- CHEM-16Acenaphthylene- Callas-l8 Phenanthrene.--

C H2n-20 C Hz r22 C 11: 2 11- Nitrogen.

Sulfur 0. 03

Naphthenoanthracene.

Pyrene Ohrysene Cliolanthrenes Beuzopyrenes--.

Total... 100. 00

Preheating zone The slurry of coal in the hydrogen-donor solvent ispassed into a preheating zone before charging it to a liquefaction zone.In the preheating zone, the slurry is heated from its temperature in themixing zone (preferably about 300 to about 350 F. when mixed with hotsolvent) to a temperature within the range from about 700 F. to about900 F. while being subjected to conditions of turbulence. The particulartemperature(s) within the range from about 700 (F. to about 900 F. towhich the slurry is heated preferably will approximate thetemperature(s) employed in the liquefaction zone with allowance for anycooling which the slurry may undergo in passing from the preheating zoneto the liquefaction zone. I

As the temperature of the slurry increases in the preheating zone to thedesired level, the particles in the hyrogen-donor slurry solventdisintegrate into smaller sizes and become .very plastic and sticky andwill agglomerate with other coal particles and with each other. In orderto minimize the problem of agglomeration, it is part of this inventionthat the slurry is maintained in a turbulent condition in the preheatingzone, at least-at temperatures above which disintegration occurs. Theturbulent regime of the slurry is a function of the Reynolds number ofthe slurry and occurs at Reynolds numbers of about 4000 and greater.High shear rates produced by high shearing stresses exerted upon theslurry are conducive to turbulent flow, and shear rates above 100 secs:-are employed, preferably being used at' a level above about 300 secs-Infinite shear rates are best. High shearing stresses are provided bypassing the slurry through the preheating zone at high superficialliquid velocities.

Liquefaction zone The preheated slurry in mixed solid and liquid phaseis passed into a lower portion of the liquefaction zone, where theconvertible portion of the coal, already disintegrated and partiallydissolved, is caused to depolymerice to form free radicals. The freeradicals can recombine to form material which is insoluble even inpyridine if a hydrogen-donor solvent prevents recombination of thefreeradicals. The degree to which recombination is prevented dependsupon the amount of donor solvent which is present. Where the donorsolvent contains about 50 weight percent of hydrogen-donor constituents,and the solvent/coal ratio is from about 0.8:1 to about 2:1, theconcentration of hydrogen-donor constitutents in the liquefaction zonecan be seen to range initially from about 22 weight percent to about 33/3 weight percent and will be depleted by the liquefaction reaction.However, molecular hydrogen can be added to the liquefaction zone topartially replenish the hydrogen-donor solvent by in situ hydrogena tionof the depleted molecules. For example, naphthenes may be hydrogenatedto Tetralins.

Thus, it is preferred to include a hydrogen-rich gas with thehydrogen-donor solvent in the liquefaction zone which provides fromabout 0.1 to about weight percent of hydrogen. Preferably, thehydrogen-rich gas is fed through the preheating zone with thehydrogen-donor solvent so that the temperature of the gas is increasedto the temperatures employed in the liquefaction zone. Inclusion of thegas in this slurry as it passes through the preheating zone does notcause appreciable hydrogenation of the coal in the preheating zone.

In accordance with this invention, the preheated slurry in mixed solidand liquid phase is plug flowed upwardly under conditions ofnonturbulent flow in a liquefaction zone in which no internal mixing,back mixing etc. is employed. Upflow occurs in the reactor at asuperficial liquid velocity which preferably is sufficient to carryupward particles having a maximum settling velocity within the rangefrom about 0.01 to about 0.04 ft./sec., or stated conversely, to permitparticles having a settling velocity greater than within the range fromabout 0.01 to about 0.14 ft./sec. to settle. Such particles are ofcourse settling through a rising liquid phase carrying a slurry orsuspension of particles. In accordance with Stokes Law, the maximumsettling velocity of a particle is therefore dependent upon the densityor specific gravity of that particle and upon the bulk suspension, thesize of the particle, and the viscosity of the bulk suspension. Theslurry in the liquefaction zone will preferably have an effectivespecific gravity within the range from about 1.4 to about 1.7. Theviscosity of the slurry in the liquefaction zone preferably will bewithin the range from about 0.1 centipoise to about 1.0 centipoise.

In the liquefaction zone, dissolution of disintegrated convertible coalparticles of various sizes, specific gravities and compositions occurs.The upflow liquid velocity of the reactor liquid is adjusted relative tothe effective specific gravity of the liquefaction zone so that thelarger convertible particles or any portion of the original coal whichmay liquefy very slowly can remain in the liquefaction zone until sizereduction allows them to be carried overhead. Certain parts of the coal(e.g. pyrite, clay and fusinite) are not liquefied in the liquefactionzone, but are instead freed from their original matrix in the zone andare present in the reacting slurry as distinct and separate particles.The upflow liquid velocity is adjusted so that the bulk of thesenonconvertible particles are contained within the liquefaction zone,from which they may be withdrawn separately instead of being carriedoverhead with the reactor liquid product. Thus, the upflow liquefactionzone provides a plug flow residence time distribution with itsassociated advantages of higher conversion and better yield andselectivity as compared to a well-mixed reactor. The liquefaction zonemay suitably be comprised of one or more vessels.

Conditions in the liquefaction zone include a temperature high enough topermit the hydrogen-transfer reaction between the hydrogen-donor solventand the moistureand mineral-free portions of the coal to occur andapressure high enough to. prevent appreciablevaporization of the solventat the temperatures employed and in consideration of the hydrogen-inputrate utilized. Suitable liquefaction conditions include a temperaturewithin the range from about 700 F. to about 1000 F., a pressure withinthe range from about 350 p.s.i.g. to about 3000 p.s.i.g.,- and anaverage liquid residence time within the range from about 5 minutes toabout 60 minutes. Thus, in a low severity process, in which, forexample, the pressure is about 500 p.s.i.g., a temperature of about 775F. may be employed in the liquefaction zone if about 1 weight percent ofhydrogen is utilized. In a moderately high severity operation, in whichthe pressure ranges, for example, from about 1500 p.s.i.g. to about 3000p.s.i.g., a temperature of about 850 F. is suitably employed wherehydrogen is used in amounts of from about 5 to about 10 weight percent.

The conditions of the liquefaction zone produce a liquefaction producttaken from the upper portion of the liquefaction zone which containsfrom about 60 to about 96 Weight percent of MEK soluble materials. ThisM-EK conversion is expressed as the percent of moisture and ash freecoal that is converted to materials which are soluble in methyl-ethylketone. It is calculated by the equation:

Percent convers1on=100 m wherein Before measuring S MEK is added to theproduct slurry as a solvent, in the ratio of 1 volume of MEK for eachvolume of product slurry. The results so obtained are referred to as MEKconversion.

As aforesaid, in the liquefaction zone the hydrogendonor solvent reactswith the free radicals resulting from depolymerization. As a result,even though hydrogen may be charged into the liquefaction zone toreplenish the donor solvent, a portion of the hydrogen-donor solventbecomes hydrogen depleted. The degree of depletion is a function of thespecific solvent and of the conditions employed. A typical recyclesolvent will contain about 50 Weight percent of compounds which willdonate hydrogen and, during about one hour within the liquefaction zonewith molecular hydrogen being added, will be depleted to the extent thatonly 25 weight percent of the solvent is made up of hydrogen-donorcompounds.

A gaseous phase product is removed from the liquefaction zone as well asthe liquefaction product. Exemplary compositions of the gas product andliquid product (without separation from solids in the slurry) are givenbelow in Table III.

TABLE III.EXEMPLARY GAS AND LIQUID PRODUCTS Liquid product Gas productCumula- Wt. tive wt. Sp. gr. Compound percent percent 60/60 F.

1. 2 IE? 21.8 7. 4 0. 9014 17. 7 14. 7 0. 9496 5. 2 22. 6 0. 9667 4. 731. 4 1. 0089 20.1 40. 2 1. 0370 15. 8 49. 0 1. 0560 0. 4 53. 4 1. 07917. 3 59. 1 Solid 0. 5 30. 9 Solid The foregoing description of theinvention will be further illustrated by a discussion of thepreferredmode of carrying out the invention, taken with adescription ofthe accompanying drawings.

7 DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of apreferred mode of carrying out this invention.

FIG. 2 is a plot depicting the change in viscosity with DESCRIPTION OFTHE PREFERRED EMBODIMENT Referring to the drawings, particulate coal isintroduced by way of line to a mixing zone 12, where it is combined witha hot hydrogenated heavy distillate recycle oil stream introducedthereinto by way of line 14 to form a slurry having a temperature ofabout 350 F. The solvent/ coal ratio in the mixing zone is preferablyabout 2:1. The slurry is conducted from the mixing zone by way of line16 and passes through a valve 18 by which about 1 weight percent ofhydrogen is metered from line 19 into the slurry. From valve 18, theslurry with hydrogen is passed by line 20 into a preheating zone 21, inwhich the temperature of the slurry is raised to approximately thetemperature to be utilized in the upfiow liquefaction zone. Thistemperature depends upon the severity of conditions employed in theupfiow liquefaction zone. For a suitable low severity liquefactionoperation, the slurry is heated to about 775 F. in the preheating zone.Conditions of turbulence including high shear rates, greater than about100 seesand providing a Reynolds Number greater than 4000 are maintainedin the preheating zone to prevent agglomeration of the slurry particlesduring swelling, dispersion and to some extent, dissolution.

From preheating zone 21, the preheated slurry in mixed solid and liquidphase is conducted by line 23 into a lower portion of an upfiowliquefaction zone 24. In a suitable low severity operation, upfiowliquefaction zone 24 is maintained at a temperature of about 875 F. anda pressure of about 500 p.s.i.g. The effective specific gravity of theliquefaction zone is preferably about 1.5. A superficial liquid velocityof about one foot per minute, sufficient to carry upward particles whichhave a maximum settling velocity of about 0.02 ft./sec. is employed.Viscosity in the zone is preferably about 1 centipoise. Residence timeof the slurry as it moves through the zone is about minutes.

The upfiow liquefaction zone 24 contains no internal mixing by stirrersor other means, and is turbulence free. The slurry moves through theliquefaction zone in a plugflow manner.

Solids having a settling velocity greater than about 0.02 ft./sec. arecollected in the bottom of upfiow liquefaction zone 24, from which theymay be withdrawn by line 25. Products of the liquefaction zone arewithdrawn from an upper portion thereof by way of line 26 for furthertreatment to obtain the useful liquid products of coal liquefaction, inaccordance with the art.

Thus, the products are suitably discharged from line 26 into agas-liquid separator 27, which is operated to permit volatile coal gasesto separate from the liquid product and to escape by way of line 28 forfurther use as desired. The liquid product from the gas-liquid separator27 is suitably discharged by way of line 29 into a fractionating zone 30which may be operated to produce a gas stream which is recovered by wayof line 31, a naphtha stream boiling up to about 400 P. which isrecovered by way of line 32 and a heavy gas oil stream boiling withinthe range from about 700 to about 1000 F., which is recovered by way ofline 33. A recycle solvent stream boiling within the range from about400 to about 700 F.

is recovered by way of line 34 for use as a hydrogen-donor solvent.

The recycle solvent is contacted in a hydrogenation zone 35 withhydrogen which is introduced by way of line 36 in the presence of ahydrogenation catalyst such' as cobalt molybdate under hydrogenationconditionssuch as a temperature of about 700 F.', a pressure of" about1350 p.s.i.g. and a space velocity of about2 weights of liquid per hourper weight of catalyst. The hydrogenated recycle solvent is thensuitably conducted by way of "line' 36 to a stripping zone 37 wherenaphtha is recovered-. from it by way of line 38. The hydrogenatedsolvent leavesv the stripping zone through line 38 and is thusdischarged back into mixing zone 12 for formation of the slurry.

The following examples further illustrate'aspects of this invention. Thefirst specifically sets out a full example of the invention. Theremaining examples show the neces-"- EXAMPLE 1 In a typical operation ofthe 'presentinvention,'two'" preheat stages were employed, one being ft.of 0.159

inch inner diameter tubing held at isothermal conditions} in heated sandbaths. The reactor itself was in-two upfiow stages, each of which had aninner diameter of 1 inches and was 30 ft. tall, with no mechanicalmixing being employed.

A 33 weight percent slurry of -l00 mesh Illinois No."

'6 coal in hydrogenated creosote oil was fed at the rate of '90 lbs./hr.(about 1 v./v./hr.) into a first preheater maintained at 500 F., at asuperficial liquid velocity of about 2 ft./ sec. and a residence time ofabout 0.2 minute, and thence into a second preheater maintained at 775F., again at a superficial liquid velocity of about 2 ft./sec'. forabout a 0.2 minute residence time. From the preheaters, the slurry wasfed to the upfiow reactors, which were operated under low severityconditions, employing a pressure within the range from about'350p.s.i.g. to about 500 p.s.i.g. The average temperature for both stagesof the reactors was 750 F. The superficial liquid velocity through thereactors was about 0.02 ft. /sec. Solids were withdrawn from the bottomof each stage of the reactor at the rate of 3-6 lbs./hr.

The liquefaction product taken from the'top of the upper reactorcontained about 6 weight percent methylethyl ketone insoluble materialsand about 19 weight per cent benzene insoluble materials. The solidswithdrawn from the bottom of each reactor stage contained about 30weight percent MEK insoluble materials, about 40 weight percent benzeneinsoluble materials and about 40 percent ash. i

Examples 2 and 3 illustrate the particular'application' of thisinvention to caking-type coals.

EXAMPLE 2 6 coal (a caking-type Eastern coal) in hydrogenated creosoteoil was continuously recycled through a slurry viscometer apparatus forabout 4% hours while information was collected on its rheologicalbehavior at various temperatures. The results of this run are shown inFIGS.- 2-4. I FIG. 2 illustrates the influence of temperature onviscosity at a shear rate of 289 secsr Observe that the viscositydecreases from about centipoise at 84 F, to about 20-21 centipoise at306 F. Note also that the viscosity does not change significantly withtemperature between about 306 and 487 F. The rheological behavior ofthis slurry was Newtonian up to 411 'F., but at higher temperatures, itwas non-Newtonian. Furthermore, the viscosity increased significantlywith temperature between 487 F. and 590 F. At 542 F., the slurry wasinitially rheopectic (viscosity increased with time) for about 5 /2minutes and then became thixotropic (viscosity -.de-

creased with time) for the next 13 minutes, until equilibrium wasobtained. The viscosity readings were off the scale of the slurryviscometer apparatus atthe shear rate utilized of 289 secs- I FIG. 3shows the reheological behavior of this slurry at 542 F. afterequilibrium was obtained. Theslurry appears to behave as a Binghamplastic. Its yieldvalue appears to be higher than 100 dynes/cm. Aturbulence produced by a shear rate in excess of about a 100 sec? isnecessary to overcome and prevent the particle agglomeration whichcauses these slurries to behave as a plastic material.

FIG. 4 shows the influence of shear rate on the viscosity of the slurryat 542 F. after equilibrium was obtained. Observe that the viscositydecreases from about 783-821 centipoise at 16 secs.* to about 125centipoises at 100 secsr and levels of about 25 centipoises at infiniteshear rate.

EXAMPLE 3 A 45 weight percent slurry of 100 mesh Illinois No. 6 coal inhydrogenated creosote oil was recycled through the same slurryviscometer apparatus utilized in Example 1, except that a high viscosityattachment was utilized. The maximum shear rate with this high viscosityattachment was 145 secs- The slurry was recycled through the slurryviscometer apparatus for 1 hour at 400 F. and then heated up to 675 F.in about 50 minutes. The results of this run are shown in FIG. 5 and inTable III.

FIG. 5 is a plot of a slurry viscosity against temperature. As inExample 1, slurry viscosity initially decreased with increasingtemperature, but at a temperature above about 550 F. in this instancesuddenly changed direction and exhibited a dramatic rise with a furtherincrease in temperature, finally peaking out, here at about 675 F. andthereafter falling off. In this example, samples from the viscometerwere taken at the beginning of the high viscosity range (Sample A), atthe maximum viscosity (Sample B), and immediately after the highviscosity range (Sample C), at the temperatures indicated by arrows inFIG. 4.

Microscopic examinations of Sample A showed no evidence of coaldissolution. Small particles were in abundance and the edges of thelarger particles were intact. Small cavities were present in the coalparticles, indicating that gas generation and subsequent coal swellingwas just beginning. MEK ash analysis indicated that no coal conversionhad occurred.

Microscopic examination of Sample B showed that some large particles haddeveloped gas vacuoles or cavities indicating softening and gasbloating. Edge destruction was evident and a smaller quantity of fineparticles than seen in Sample A were observed, indicating that coaldissolution had begun. However, MEK ash conversion analysis againindicated that no conversion or upgrading had occurred.

Microscopic examinations of Sample C showed that no identifiable coalparticles existed and that the sample consisted of reagglomeratedmaterial. It appeared as if the coal may have been dispersed asfragments of collodial material, but these colloids then appeared to bereagglomerated. MEK ash conversion was 6.9%

Table IV shows the influence of shear rate on the maximum slurryviscosity in the swelling range.

TABLE IV Influence of shear rate on maximum slurry viscosity in swellingrange of Illinois No. 6 coal in hydrogenated creosote oil, at 667 F.

Shear rate (sec- Viscosity (cp.)

Examples 2 and 3, taken together, and especially FIGS. 2-5, show thatthe sharp increase in the viscosity of the slurry as the temperature isincreased is due to a swelling of the coal particles. Thisswelling isapparently the initial stage 'of-"the coal disintegration/dissolutionprocess and results in non-Newtonian slurry characteristics. As the coaldisintegration and dissolution proceeds, the viscosity decreases again.High shear rates (turbulent fiow conditions) are elfective incontrolling agglomeration of the plastic coal particles, as evidenced bythe decrease in slurry viscosity at high shear rates.

Having fully and particularly disclosed our invention, including apreferred mode of carrying it out, what is desired by Letters Patent isdefined by the appended claims.

We claim:

1. A process of liquefying coal, which comprises:

(a) introducing (1) a slurry (la) of coal particles suspended in (1b) ahydrogen-donor solvent maintained in liquid phase (2) into a preheatingzone (2a) where the slurry is heated to a temperature within the rangefrom about 700 F. to about 950 F.

(2b) and subjected to conditions of turbulence (2c) for a residence timesufficiently long to cause the coal particles to disintegrate and topartially dissolve without agglomerating,

(b) passing the preheated slurry in mixed solid and liquid phase (1)upwardly through (2) a turbulence-free liquefaction reaction zonemaintained at (2a) a temperature high enough to permit ahydrogen-transfer reaction to occur between the hydrogen-donor solventand moistureand mineral-free portions of the coal, and

(2b) a pressure high enough to prevent appreciable vaporization of thesolvent,

(3) at a superficial liquid velocity sufficient to support coal finesand to permit the settling of heavier particles,

(4) for a residence time sufiicient to produce a liquefaction product inan upper portion of the reaction zone, and

(c) withdrawing (1) from an upper portion of the liquefaction reactionzone (la) liquefaction product including at least 70 weight percentmethyl-ethyl ketone soluble materials, and

(2) from a lower portion of the reaction zone,

(2a) undissolved solids settled from the reaction zone.

2. The process of claim 1 in which the slurry is comprised ofcaking-type coal particles.

3. The process of claim 1 in which the conditions of turbulence in saidpreheating zone include a Reynolds number of at least 4000.

4. The process of claim 1 in which the superficial liquid velocity insaid liquefaction zone is within the range from about 0.01 to about 0.04ft./sec.

5. A process of liquefying coal which comprises continuously:

(a) forming a slurry of (1) coal particles having a size range of about8 mesh (Tyler) and smaller 2) in a hydrogen-donor solvent (2a) boilingwithin the range from about 300 F. to about 900 F. and

(2b) containing at least 30 weight percent of .hydrogen donors chosenfrom the group consisting of C to C Tetralins, indane, C and ciacenaphthenes, ditetra-, and

octahydroanthracene and tetrahydroacenaphthen e, and mixtures of two ormore thereof, I

[(3) at a solvent/coal ratio within the range from I about 0.8:1 toabout 2: l,

(b) passing the slurry through a preheating zone (1) in which the slurryis heated to a temperature within the range from about 700 F. to about900 F.,

(2) under conditions of turbulent flow,

(3) whereby disintegration and partial dissolution of the coal particlesoccurs therein,

() flowing the preheated slurry in mixed solid and liquid phase underconditions of non-turbulent plug flow upwardly through an unmixedliquefaction zone (1) with a hydrogen-rich gas providing from about 0.1to about weight percent of hydrogen (2) under liquefaction conditionsincluding (2a) a temperature within the range from about 700 F. to about1000 R,

(2b) a pressure within the range from about 350 p.s.i.g. to about 3000p.s.i.g.

(2c) for an average liquid residence time within the range from about 5minutes to about 60 minutes,

(3) at a superficial liquid velocity sufiicient to carry upwardparticles which have a maximum settling velocity within the range fromabout 0.01 to about 0.04 ft./sec., and

(d) withdrawing (1) from an upper portion of the liquefaction zone (1a)a liquefaction product containing from from about 70 to about 96 weightpercent of methyl-ethyl ketone soluble materials and (2) from a lowerportion of the liquefaction zone (2a) solids consisting essentially offrom about Weight percent to about weight percent of methyl-ethyl ketoneinsoluble materials, and from about 35 to about weight percent of ash.

6. The process of claim 5 in which the slurry is comprised ofcaking-type coal particles.

7. The process of claim 5 in which the slurry in the preheating zone hasa Reynolds Number greater than about 4000.

8. The process of claim 5 in which the slurry in the preheating zone issubjected to a shear rate greater than about 100 secsf p f 9. Theprocess of claim 5 in which the said slurry in said liquefaction zonehas an effective specific gravity "within the range from about 1.4 toabout 1.7.

10. The process of claim 5.in which the viscosity of the slurry in theliquefaction zone is within the range from about from about 0.1centipoise to about 1.0 centipoise.

11. The process of claim 5 in which the superficial liquid velocity inthe liquefaction zone is about one foot per minute.

12. A process for liquefying caking-type coals, compris- (a) introducinga slurry of caking-type coal particles in a hydrogen-donor solvent inliquid phase into a preheating zone under conditions of turbulenceincluding a shear rate exceeding 100 secs- (b) heating said slurry insaid preheating zone under said conditions of turbulence to atemperature within the range from 700 F. to 900 F., efiective to causesaid coal particles to undergo disintegration and partial dissolutionwithout agglomeration,

(c) passing said preheated slurry in mixed solid and liquid phaseupwardly in plug flow through a turbulence-free liquefaction zone at atemperature within the range from about 700 F. to about 950 F.,' a'pressure within the range from-about 300 p.s.i.g. to about 3000 p.s.i.g.for a residence time of from about 5 minutes to about minutes at asuperficial liquid velocity sutficient to carry upward particleshaving'a settling velocity within the range from about 0.01 ft./ sec. toabout 0.04 ft./sec.,

(d) withdrawing a liquefaction product comprising at least about weightpercent of methyl-ethylket'one UNITED STATES PATENTS 9/1967 Bull et al2088 OTHER REFERENCES Alan S. Foust et al.,' Principles of UnitedOperations, John Wiley, New York, p. 141, 1966, Fourth Printing.

PAUL M. COUGHLAN, JR., Primary Examiner V. OKEEFE, Assistant Examiner I

